We recently answered a few questions about how certain nicknames/name forms came to be associated with their full forms over on FB. These comments seemed to generate enough interest that we figured we’d expand on them here in a couple of posts.
First up is a question that has probably puzzled a lot of English speakers at some point or another — just how did Peggy come to be a nickname of Margaret? Or Dick from Richard, Bob from Robert, Ted and Ned from Edward, etc.? In this post we’ll focus on Peggy and Margaret, but the same pattern of development happened for all these names. (We’ll make use of the terminology for nicknames that we introduced here).
So, how does Margaret become Peggy?
Margaret is the radiconym; take it and cut the name down to the first syllable, and you get Marg. In certain dialects, that r is going to be very lightly pronounced, giving us Mag. Magge (pronounced with two syllables) can be found in England as early as 1200, and not much later after that, you can find that hypocoristic form augmented with a diminutive suffix: Magota 1208 (this is a Latin form and would’ve been Magot in the vernacular). (We’ll give you three guesses as to why this name is no longer popular today….). By the end of the century, there are examples of the -a- shifting to -e-, e.g., Megge 1254, 1275, 1279, etc. You can also see it in Megota 1309 (also Latinized).
So that gets us Meg. From there, Peg is straightforward: It’s a rhyme.
The shift from something like Magge, Megge, or Pegge to Maggie, Meggie, or Peggy comes in the 16th C with the Great Vowel Shift — what used to be an unstressed schwa sound shifts to \ee\. And then eventually the spelling caught up, but that happened late enough that we don’t have any specific data. (Yet.)
References
Reaney & Wilson, s.nn. Dick, Dicken, Dicketts, Madge, Maggot.
Withycombe, s.nn. Edward, Margaret, Robert.
Dictionary of Medieval Names from European Sources 